Effect of the notched foreign object damage depth on the HCF strength of titanium alloy TC11

Abstract

In this study, the effects of different incident foreign object damage (FOD) depths on the high-cycle fatigue (HCF) performance of TC11 titanium alloy specimens with compressor leading edge blades were studied. FOD values were obtained through high-speed ballistic impact tests at different aiming positions under the same impact conditions. HCF tests of smooth and FODed specimens were conducted via the step-loading test method, and the HCF strength was determined via experiments and numerical analysis. The results indicated that with increasing damage depth, the stress concentration factor significantly increased. There occurred greater material losses on the exit side of the resultant notch damage than those on the incident side. The maximum damage depth ranged from 0.23 to 1.51 mm, and the fatigue strength of the FODed specimens reached approximately 21.77–84.99 % of that of the smooth specimens. With increasing depth, the material loss increased, and the fatigue strength decreased. According to the Kf = 3 empirical criterion for FOD tolerance design, the determined serviceable limit of notch-type damage was 0.84 mm, which is expected to be useful for quick assessment of the notch-type FOD degree of TC11 titanium alloy leading edge blades.